Most people in the medical field are probably familiar with medical gas, but many people outside of this industry may not know what a medical gas is and why it is so important. This article will cover what you need to know about medical gas.
1. What is medical gas?
Medical gas is single or mixed gases supplied centrally by medical piping systems for the treatment, diagnosis, or prevention of patients’ diseases, or for driving surgical tools and instruments, etc. In applications they also include medical vacuums and gases used for medical experiments and bacterial and embryonic cultures, etc. The most common types of medical gases are oxygen, air, vacuum, nitrous oxide, carbon dioxide, anaesthetic gases, nitrogen, etc. Medical gases are used in a variety of environments, including hospital operating rooms, emergency rooms, intensive care units, ambulances, and clinics.
2. Introduction to commonly used medical gas
With the development of medical and health care, the variety and demand of medical gases have been increasing, and the quality of medical gases has also put forward higher requirements, and their application to medical fields has been expanding. In this article, we will introduce the uses and production methods of some common medical gases.
2.1 Medical Oxygen
2.1.1 Medical oxygen applications
Medical oxygen is the most common and important medical gas, and there are three main medical uses for oxygen: emergency oxygen infusion, oxygen therapy, and oxygen health care.
(1). Emergency oxygen infusion. It is used to rescue critically ill patients and accident victims by giving pure oxygen inhalation at a high flow rate for a short period of time to prevent irreversible damage to the body caused by acute hypoxia. For example carbon monoxide poisoning, electrocution, drowning, first aid patients, etc. The oxygen used for emergency oxygen delivery must meet the quality requirements of the relevant national standards or international standards for oxygen.
(2). Oxygen therapy. Oxygen therapy is used to increase the concentration of oxygen in the inhaled gas by supplementing oxygen, to increase the oxygen content of the arterial blood and improving the oxygen supply, collectively known as oxygen therapy. Of these, those used to correct pathological hypoxia as an adjunct to the treatment of disease are called oxygen therapy. The American Thoracic Society (ATS) and the European Resuscitation Council (ERC) suggest that an effective minimum oxygen concentration should be given during the advanced life support phase after resuscitation (30% oxygen concentration is appropriate for long-term oxygen therapy).
(3) Oxygen health care. It is used to supplement physiological hypoxia in heavy brain workers, middle-aged and elderly people, pregnant women and patients recovering from chronic diseases, as well as to supplement various environmental hypoxia as a means of preventing hypoxia, called oxygen health care. In addition, oxygen also has the effect of enhancing memory, reducing skin laxity, and increasing skin elasticity.
2.1.2 Medical oxygen production
There are many ways to produce oxygen, this article describes three ways to produce oxygen by cryogenic air separation, pressure swing adsorption, and membrane separation.
(1). Cryogenic Air Separation
The cryogenic air separation method of oxygen production is based on the difference in the boiling points of oxygen (boiling point -183°C) and nitrogen (boiling point -196°C) in the air mixture, the use of liquefaction and distillation to separate the oxygen and nitrogen to obtain oxygen.
In the process of oxygen production by cryogenic air separation, the oxygen product is generally produced from the raw air through air filtration, compression, pre-cooling, purification, pressurization, expansion, distillation, product storage, and other basic processes.
Cryogenic air separation is a traditional method of oxygen production, with large equipment, complex structure, equipment investment, and management costs, and is generally used in professional oxygen plants. The products of oxygen production by cryogenic air separation are gaseous oxygen and liquid oxygen. The gaseous oxygen is filled into the cylinder through the filling ramp, the liquid oxygen is stored in the low temperature liquid rest storage tank, it can be sent directly to the user by tanker truck to fill the user’s low temperature liquid storage tank.
(2) Pressure Swing Adsorption
In the hospital, usually use the medical molecular sieve oxygen equipment to produce oxygen-rich air, it is the air as raw material, molecular sieve as adsorbent to produce oxygen concentration of 90% to 96% (oxygen-enriched air) by the pressure swing adsorption method, mainly for health care purposes.
Pressure Swing Adsorption is a method of oxygen separation using molecular sieve adsorbents for the selective adsorption of oxygen and nitrogen components in the air (referred to as PSA). It is a semi-permanent adsorbent with zeolite as the main raw material and a specially processed crystal structure with uniform micropores and special properties. The separation of oxygen and nitrogen by molecular sieves is based on the different diffusion rates of these two gases with different polarities on the surface of the molecular sieve, thus constituting a unique adsorption selectivity. The molecular sieve has the property of increasing the adsorption capacity of nitrogen when pressurized and decreasing it when depressurized.
When air flows through an adsorption tower equipped with molecular sieves, the molecular sieves preferentially adsorb the nitrogen component, the last adsorbed oxygen is enriched and exported through the molecular sieves, and the adsorbed nitrogen is desorbed through a reduced pressure discharge. The pressure swing adsorption process (PSA) is a process of several stages of adsorption, pressure equalization, and desorption. According to the operating pressure during adsorption, it can be subdivided into three processes: PSA, VPSA, and VSA. The existing medical molecular sieve oxygen production equipment mainly adopts PSA, VPSA two processes. Medical molecular sieve oxygen equipment is usually set up with two or four adsorption beds (or adsorption towers) to alternately carry out adsorption, homogenization, and desorption cycles to continuously output oxygen.
(3) Membrane separation method for oxygen production
In recent years, with the development of science and technology, membrane separation technology has been gradually applied in the production of oxygen-rich air. The technology is to make the air pass through the membrane with the function of oxygen enrichment under a certain pressure, through multi-stage separation to achieve the physical separation of oxygen and nitrogen, so as to obtain oxygen.
The permeation of gases through hollow polymer films is a complex process in which the gas molecules are first adsorbed onto the surface of the membrane and dissolved, then diffused through the membrane and finally desorbed from the other side of the membrane.
The concentration of oxygen produced by this method is not high, so in the early days it was mainly used for oxygen-rich combustion technology, such as in large boilers, medium-sized boilers for industrial use, boilers for heating, boilers for ship power plants, etc. Oxygen-rich air produced by membrane separation was used instead of ordinary air for combustion.
With the development of technology, in order to increase the oxygen content, the pressure swing adsorption oxygen production and membrane separation are used to jointly produce oxygen, and the oxygen content can be increased to 99.5%. This technology first uses the pressure swing adsorption process to produce oxygen-enriched air as raw material, and then Oxygen is purified by conventional organic membrane separation methods or continuous membrane column (CMC) methods. However, the extra compression power of this separation system makes the energy consumption very high, and the special membrane separator required for the CMC cycle is also very expensive, which restricts its wide application.
2.2 Medical Vacuum
2.2.1 Medical vacuum applications
Medical vacuum, also known as negative pressure suction, is mainly used to provide negative pressure to operating rooms, resuscitation rooms, treatment rooms, and patient rooms outlets to generate suction for medical use. Medical vacuum should not be used in Class III or IV biosafety laboratories or in radioactively contaminated sites; medical vacuum in independent infectious disease departments and dentistry should be used separately and should not be shared with general departments.
2.2.2 Medical vacuum production
Equipment for obtaining vacuum can be broadly divided into three categories: electric suction devices, manually driven suction devices; and suction devices driven by negative pressure sources or pressure sources. Medical vacuum system is used exclusively for the removal of patient fluids and is provided mainly by means of medical central suction systems.
Medical vacuum is produced using a vacuum pump. A vacuum pump is a device that uses mechanical and physical methods to pump air in a closed space (e.g. containers and pipes) in order to obtain and maintain a vacuum. At present, the main vacuum pumps used are variable volume rotary vacuum pumps, including liquid ring, rotary vane, rotary gear, scroll, screw, roots, sidestream, and centrifugal vacuum pumps. Among them, liquid ring and rotary vane vacuum pumps are commonly used. Liquid ring vacuum pumps are more commonly used, generally using water ring vacuum pumps with direct connection structure, and rotary vane vacuum pumps generally using oil rotary vacuum pumps.
The difference between dental vacuum and medical vacuum is mainly the difference in vacuum pressure, the vacuum pressure of medical vacuum is high, the vacuum pressure of dental vacuum is relatively low. Dental vacuum is obtained in the same way as medical vacuum, the equipment includes liquid ring vacuum pumps, vacuum tanks, check valves, etc. Vacuum fan units can also be used. To avoid cross-contamination, the dental vacuum equipment should be set up separately and amalgam separation devices should be installed as required.
2.3 Medical Air
2.3.1 Medical air applications
Air is essential for the survival of plants and animals on earth, and is essential for animal respiration and plant photosynthesis. In industry, air has a wide range of uses. In medicine, medical air includes medical air, instrument air, medical synthetic air and dental air, which is mainly used to drive surgical tools and to accompany treatment, such as nebulised therapy.
2.3.2 Medical air production
Medical air is the air used for medical purposes. The air is compressed and purified by pumping atmospheric air through an air compressor to obtain purified air with a limited concentration of contaminants and a certain pressure for medical, instrument and dental use. Depending on the application, the pressure used ranges from 0.4 to 1.0 MPa.
The main types of air compressors used today are piston, screw, rotary gear, and scroll air compressors, which are designed to provide a continuous source of air at a certain pressure. The air is cleaned mainly by drying and filtering with various precision filters.
The difference between medical air, instrument air and dental air is mainly due to the difference in working pressure and the moisture content of the gas. The pressure of instrument air is relatively the highest (≥800kPa), dental air (the second highest pressure (≥500kPa), the pressure of medical air is relatively the lowest (≥400kPa), the choice of air compressor output pressure should match; medical air moisture content ≤575mg/m³, dental air moisture content ≤780mg/m³, instrument air moisture content ≤50mg/m ³. Therefore, an adsorption dryer is required for the production of instrument air. Instrument air can also be replaced by nitrogen in hospitals.
Medical synthetic air is made by mixing medical oxygen and medical nitrogen in a ratio of 21% oxygen and 79% nitrogen.
2.4 Carbon dioxide
In medical use, carbon dioxide is mainly used in pharmaceutical excipients and medicines, etc.
(1) Used as a pharmaceutical excipient. Mainly used as an air replacement agent, pH adjuster, and aerosol throwing agent, such as in sodium bicarbonate injection filled with CO2, adjusting the solution pH: in the preparation of vitamin C injection process by CO2, reducing the contact between the drug and the air. Medical carbon dioxide is widely used in various pharmaceutical companies.
(2) As a respiratory stimulant. Clinically, it can be used to treat apnoea and hypocapnia in newborns. Medical carbon dioxide is an important physiological stimulus for maintaining normal respiration in the human body and plays a regulatory role in respiratory movements. Inhaling the right amount of CO2 causes significant vasodilation and increases blood volume. This effect can even replace vasodilating drugs and help humans to treat certain diseases. If a person inhales pure oxygen for a prolonged period of time, a low concentration of carbon dioxide in the body can lead to respiratory arrest. For this reason, a mixture of 5% carbon dioxide and 95% oxygen is used clinically for the treatment of carbon monoxide poisoning, drowning, shock, alkalosis, or anesthesia. Carbon dioxide can be made into dry ice by pressurization (5.2 standard atmospheres) and cooling (below -56.6°C). Medically dry ice is used for cryotherapy, for the treatment of cataracts, vascular disease, etc.
(3) Other roles. Medical carbon dioxide can also be used to inflate the abdominal cavity and colon for laparoscopy and fibre colonoscopy. Carbon dioxide can also be used for medical equipment instruments for standard gas, calibration gas; sterilization of apparatus for sterilization gas diluent and antiseptic, refrigerant, local anesthetic, extractant, laboratory culture bacteria (anaerobic bacteria), solid carbon dioxide can also be used in the production of penicillin; in addition, carbon dioxide is also widely used in a variety of medical treatment and clinical experiments, as a variety of medical gas mixture of component gas and balance In addition, carbon dioxide is widely used in various medical treatments and clinical experiments as a component and balance gas in various medical gas mixtures.
2.5 Nitrous Oxide(Laughing gas)
In medical practice, it is mainly used as an anaesthetic for dental, ophthalmic, obstetrical and gynaecological and surgical procedures, and is administered to patients by closed means or by breathing machine. It does not require any degradation or biotransformation in the body and most of the nitrous oxide is excreted with the patient’s exhalation without any accumulation effect.
The use of a mixture of nitrous oxide and oxygen as an anaesthetic has the following advantages: short induction period, only 30-40 seconds are required for inhalation to produce analgesia. The analgesic effect is strong but the anaesthetic effect is weak, the patient is awake, complications from general anaesthesia are avoided and recovery from surgery is rapid.
Nitrous oxide and carbon dioxide are used in small quantities in hospitals and are generally purchased externally in cylinders, they are produced by specialised gas production plants and generally require a pharmaceutical manufacturing licence for their production.
2.6 Other gases
In addition to the common gases mentioned above, nitrogen, argon, helium, neon, krypton, radon, ozone, carbon monoxide, hydrogen, ethylene oxide, chlorine, acetylene and methane are also used to varying degrees in medical applications.
3. Where can I find out more about medical gases
Amcaremed as a professional medical gas company, we specialize in providing medical gas services to hospitals and can help hospitals with all aspects of medical gas systems, our goal is to provide you with quality products and excellent customer service at competitive prices.
If you have any questions about medical gases, please feel free to contact us.